Mario Manassero

New nickel–carbon dioxide complex: synthesis, properties, and crystallographic characterization of (carbon dioxide)-bis(tricyclohexylphosphine)nickel

[Ni(CO2)(PCy3)2],0·75(C7H8), where Cy = cyclohexyl, can be made either by treating [Ni(PCy3)3] or [{Ni(PCy3)2}2N2] with CO2 in toluene, or by direct reduction of [NiBr2(PCy3)2] with sodium sand under CO2; the complex is planar, the CO2 ligand possesses bent geometry and is co-ordinated through the carbon atom and one of the oxygen atoms.

Novel atropisomeric phosphorus ligands: 4,5-dihydro-3H-dinaphtho[2,1-c;1′,2′-e]phosphepine derivatives

Abstract Atropisomerically pure (S)-4-phenyl-4,5-dihydro-3H-dinaphtho[2,1-c;1′,2′-e]phosphepine 2b has been obtained by resolution of the racemic compound with an enantiopure palladium complex and its absolute configuration has been determined by X-ray analysis; it is an effective chiral ligand for the asymmetric hydroformylation of styrene with rhodium catalysts.

Preparation and characterization of palladium(II) and platinum(II) complexes with bis(pyrazolyl)alkanes. crystal and molecular structures of [Pd2(pz)22][BF4]2 and of [PdCl2{(CH3)2C(pz)2}] (pzH = pyrazole), a new example of a Pd⋯HC agostic interaction

Abstract Neutral and cationic complexes of general formulae (LL)MCl 2 (M = Pd, (LL) = CH 2 (pz) 2 ( 1 ); CH 2 (3,5-Me 2 pz) 2 ( 2 ); (CH 3 ) 2 C(pz) 2 ( 3 ); M = Pt, (LL) = CH 2 (pz) 2 ( 4 ); CH 2 (3,5-Me 2 pz) 2 ( 5 ) and (LL) 2 M] 2+ (M = Pd, (LL) = CH 2 (pz) 2 ( 6 ); CH 2 (3,5-Me 2 pz) 2 ( 7 ); (CH 3 ) 2 C(pz) 2 ( 8 ); M = Pt, (LL) = CH 2 (pz) 2 ( 9 ); CH 2 (3,5-Me 2 pz) 2 ( 10 ) have been prepared and characterized by IR and 1 H NMR spectroscopy. The structures of 3 and 6 have been determined by X-ray diffraction; in both complexes the bis-(pyrazolyl)alkanes act as chelating ligands but the coordination around the palladium atom in the complex 6 is strictly square-planar whereas in 3 it is a slightly distorted towards pyramidal, with a significant Pd⋯HC agostic interaction. The six-membered rings in both the complexes adopt a boat-type conformations.

[Au2(phen2Me)2(μ-O)2](PF6)2, a Novel Dinuclear Gold(III) Complex Showing Excellent Antiproliferative Properties

A novel dioxo-bridged dinuclear gold(III) complex with two 2,9-dimethylphenanthroline ligands was synthesized and thoroughly characterized. Its crystal structure was solved, and its solution behavior assessed. Remarkably, this compound revealed excellent antiproliferative properties in vitro against a wide panel of 36 cancer cell lines, combining a high cytotoxic potency to pronounced tumor selectivity. Very likely, these properties arise from an innovative mode of action (possibly involving histone deacetylase inhibition), as suggested by COMPARE analysis. In turn, electrospray ionization-mass spectrometry studies provided valuable insight into its molecular mechanisms of activation and of interaction with protein targets. Gold(III) reduction, dioxo bridge disruption, coordinative gold(I) binding to the protein, and concomitant release of the phenanthroline ligand were proposed to occur upon interaction with superoxide dismutase, used here as a model protein. Because of the reported results, this new gold(III) compound qualifies itself as an optimal candidate for further pharmacological testing.

Palladium(II) and platinum(II) derivatives with chiral 2,2′-bipyridines. X-ray structure of C18H15ClN2Pd; C- and N-intramolecular coordination in a six-membered metallacycle

Abstract The reactions of (+)-( S )-5-s,butyl-2,2′-bipyridine (LH) and 6-(1-methylbenzyl)-2,2′-bipyridine (L′H) with Na 2 [PdCl 4 ] and K 2 [PtCl 4 ] give the 1 : 1 adducts (LH)MCl 2 (M = Pd, 1 ; M = Pt, 2 ) and the metallated species (L′)MCl (M = Pd, 3 ; M = Pt, 4 ), respectively. In complexes 3 and 4 , the deprotonated bipyridine behaves as a tridentate ligand; there is coordination to the metal through the two nitrogen atoms and the ortho -carbon atom of the phenyl ring to give a six-membered metallacycle. The X-ray structure of complex 3 shows that the coordination around the palladium atom is distorted towards tetrahedral from the usual square-planar geometry.

2-Diphenylphosphino-2′-diphenylphosphinyl-1,1′-binaphthalene (BINAPO), an axially chiral heterobidentate ligand for enantioselective catalysis

Abstract Racemic 2-diphenylphosphino-2′-diphenylphosphinyl-1,1′-binaphthalene (BINAPO) 5 has been prepared in four steps from 1,1′-binaphthalene-2,2′-diol (BINOL) 1 and has been resolved with the aid of the C,N-cyclopalladated complex with N,N-dimethyl (S)-1-(1-naphthyl)ethylamine 6. P,O-chelate binding to palladium occurs in solution and this is confirmed in the solid state by X-ray analysis. (S)-BINAPO is an immediate precursor of (S)-BINAP and is itself an effective chiral inducer for the Pd-catalyzed asymmetric hydrosilylation of styrene (over 70% e.e.).

Synthesis and characterization of gold(III) adducts and cyclometallated derivatives with 6-benzyl- and 6-alkyl-2,2′-bipyridines

The reaction of a series of 6-substituted-2,2′-bipyridines HL (N2C10H7R, R = CH2Ph, CHMePh, CMe2Ph, CH2Me, CMe3 or CH2CMe3) with HAuCl4 or Na[AuCl4] has been investigated. Under different experimental conditions, salts [H2L][AuCl4], adducts [Au(HL)Cl3] or cyclometallated derivatives [Au(L)Cl][X](X = AuCl4, BF4 or PF6) have been isolated. The cyclometallated species arise from direct activation of a C–H bond either of a phenyl or a methyl substituent. The structures of an adduct [Au{N2C10H7(CHMePh)-6}Cl3] and two metallated species [Au{N2C10H7(CMe2C6H4)-6}Cl][AuCl4] and [Au{N2C10H7(CMe2CH2)-6}Cl][BF4]·0.5H2O have been determined by X-ray diffraction. In the adduct the gold atom is bonded to the nitrogen atom of the unsubstituted pyridine ring: a long-range interaction with the other nitrogen atom is observed, Au ⋯ N 2.758(4)A. In the two cyclometallated species the bipyridines act as tridentate N,N,C anions, giving a [5,6] and a [5,5]-fused ring system, respectively. In [Au{N2C10H7(CMe2C6H4)-6}Cl]+ the hexaatomic N,C ring adopts a boat-like conformation: the structure reveals a rather short interaction between one hydrogen of the Me group in axial position and the gold atom, Au ⋯ H 2.62 A. The pentaatomic N,C ring in [Au{N2C10H7(CMe2CH2)-6}Cl]+ is not planar: the co-ordination around the gold atom is essentially square planar. The new cyclometallated complexes [Au(N,N,C)Cl]+ are compared with those derived from similarly substituted pyridines described previously.

Four μ4-oxo-bridged copper(II) complexes: magnetic properties and catalytic applications in liquid phase partial oxidation reactions

Four copper(II) complexes, [Cu(4)(O)(L(n))(2)(CH(3)COO)(4)] with N(2)O-donor Schiff-base ligands, where HL(1) = 4-methyl-2,6-bis(cyclohexylmethyliminomethyl)phenol for complex 1, HL(2) = 4-methyl-2,6-bis(phenylmethyliminomethyl)phenol for complex 2 x CH(3)CN, HL(3) = 4-methyl-2,6-bis(((3-tri-fluoromethyl)phenyl)methyliminomethyl)phenol for complex 3, HL(4) = 4-methyl-2,6-bis(((4-tri-fluoromethyl)phenyl)methyliminomethyl)phenol for complex 4, were synthesized and characterized by elemental analysis, FT-IR, UV-vis spectroscopy and finally by single crystal X-ray diffraction study. X-Ray analysis reveals that all of these are mu(4)-oxo-bridged tetrameric copper(II) complexes. Four copper atoms arrange themselves around an oxygen atom tetrahedrally. Magnetic susceptibility measurements show the existence of very strong antiferromagnetic coupling among these ions (J = -210.1 to -271.3 cm(-1)), mediated by the oxygen atoms. Catalysis of the epoxidation of cyclohexene, styrene, alpha-methylstyrene and trans-stilbene by these complexes has been carried out homogeneously as well as heterogeneously by immobilizing the metal complexes over 2D-hexagonal mesoporous silica. The results obtained in both the catalytic conditions show that the olefins are converted to the respective epoxides in good yield together with high selectivity.

Stereochemistry of tetrahedral complexes of group VIII metals. Crystal and molecular structures of dinitrosylcarbonyltriphenylphosphineiron, Fe(NO)2(CO)(PPh3), and of dinitrosylbis(triphenylphosphine)iron, Fe(NO)2(PPh3)2

Single crystal X-ray structures of Fe(NO) 2 (CO)(PPh 3 ) (I) and of Fe(NO) 2 (PPh 3 ) 2 (II) have been determined. Compound (I) form triclinic crystals of space group P , with cell constants a 10.96(1)», b 10.20(1)», c 10.45(1)», α 115.84(8)°, β 117.33(8)°, γ 78.90(8)°, U 933.4» 3 , Z 2. Compound (II) forms monoclinic crystals of space group P 2/ c with cell constants a 11.70(1) », b 8.20(1) » c 17.24(2) », β 106.60(8)°, U 1584.6 » 3 , Z 2. Both cystals contain discrete molecules of distorted tetrahedral geometry. In compound (I) the CO and NO ligands are disordered; the principal bonding parameters are: FeC/N 1.709 », C/NO 1.148 », FeC/NO 177.9°, FeP 2.260(3) », C/NFeC/N 103.9° and PFeC/N 114.4°. In compound (II), which possesses C 2 symmetry, the principal bonding parameters are: N 1.650(7) », NO 1.19(1) », FeNO 178.2(7)° NFeN 123.8(4)°, FeP 2.267(2) », PFeP 111.9(1)°. These values are compared with those found in other tetrahedral complexes of Group VIII metals and discussed in terms of π metalligand interactions.

Crystal structure of [Me3NCH2Ph][Fe4(CO)13H]. A ‘butterfly’ metal cluster with an unusually bonded carbonyl group

A single-crystal X-ray analysis has shown the [Fe4(CO)13H]– anion to contain a butterfly arrangement of metal atoms; twelve carbonyl groups are terminally bonded, three to each iron atom, whereas the thirteenth carbonyl group interacts with all the four iron atoms and behaves as a four-electron ligand.